Liquid blanketed chlorate blasting agent



United States Patent LEQUID BLANKETED CEHJORATE' BLASTENG AGENT Melvin A. (look, Thomas K. Collins, Wallace 1). Pack, and Noel L. Cook, Salt Lake City, Utah, assignors to llnterrnountain Research and Engineering (Ioinpany, ind, Salt Lake (Iity, Utah, a corporation of Utah No Drawing. Filed May 10, 1961, Ser. No. lllll fibl 7 Claims. (Cl. 149-77) This invention relates to explosive compositions and more particularly to blasting agents comprising sodium chlorate blanketed with a liquid fuel and methods of preparing the same.

Chlorates, particularly potassium chlorate, have been proposed in the past as a principal ingredient of explosives but have not met with widespread use because of their hazardous nature. Thus, prior chlorate-containing explosives have been found to be very sensitive to shock, heat, and impact and accordingly were very dangerous to prepare and utilize.

It has now been discovered that sodium chlorate, hitherto thought unsuitable for blasting explosives because of its hygroscopic properties, may be utilized to prepare liquid blanketed blasting agents which are safe to compound and use and which are more powerful and more economical than prior art explosives based on potassium chlorate. It has been found that liquid blanketed sodium chlorate explosives which have a zero oxygen balance and all available free space filled with liquid fuel provide safe and effective blasting agents. The prior art attempts to provide a liquid blanketed chlorate blasting agent, such as illustrated in US. Patents 243,432, 289,756, and 1,240,272, were not successful due to erratic and hence unsafe performance, because the resulting explosives did not possess zero oxygen balance and have all available free space filled with liquid fuel.

It is accordingly among the primary objects of this invention to provide economical blasting agents of high bulk strength and minimum hazard in their preparation and use. The blasting agents of the invention comprise sodium chlorate particles and a liquid fuel, said mixture having substantially zero'oxygen balance and all available free space between the sodium chlorate particles filled with the liquid fuel.

The term blasting agent as used herein and in commercial explosives technology refers to detonating explosives which cannot be detonated with commercial blasting caps, such as #6 or #8 electric blasting caps, but require boosters. A booster is a cap-sensitive or detonating fuse-sensitive high explosive which produces a detonating wa ve sufficiently powerful to detonate the capinsensitive explosive.

The term zero oxygen balance as used herein is computed on the basis that all combustible elements contained in the explosive are oxidized to maximum state. For example, in an explosive containing the elements carbon, hydrogen, nitrogen, and oxygen, zero oxygen balance is achieved when the products of combustion consist of carbon dioxide, water, and nitrogen. The oxygen balance of an oxidizing agent is a positive quantity equal to the fraction of available oxygen contained in the oxidizing agent. Thus, for example, the oxygen balance of sodium chlorate is +045. The oxygen balance of a fuel is a negative quantity equal to the weight of oxygen required to burn one part by weight of the fuel to its completely oxidized state, The oxygen balances and densities of some liquid fuels are as follows:

Available free space, as used herein, refers to the fraction of volume of a mass of particulate oxidizing agent that is accessible to a liquid fuel. in other words, it represents the volume, in cubic feet, of liquid fuel which fills up all the void between the particles of a cubic foot of solid oxidant such as sodium chlorate. It will be understood that the particle size and particle size distribution of the particulate oxidant will determine the fraction of available free space. The available free space ofany particulate solid is readily determ nable experimentally. It will be noted that many particulate materials also possess unavailable or non-accessible free space, such as air spaces locked inside the individual particles thereof. The free space concerned here however is that volumetric fraction accessible to a liquid fuel.

There are two methods for attaining an oxygen balanced blanketed blasting agent. One method involves adjustment of the liquid fuel oxygen balance to conform to the following equation:

where Thus for a given solid oxidant, the quantities B d and f are known and a liquid fuel must be chosen to satisfy the following equation:

It is apparent that two or more liquid. fuels may be blended to achieve the desired product B dj of Equation 2. In addition, inert liquids, such as water, may be blended with a liquid fuel to obtain a fuel having the desired product B d The other method of achieving an oxygen balanced blanketed blasting agent involves adjustment of the available free space of the solid oxidant by the addition thereto of an inert solid to increase the unavailable free space and hence decrease the available free space. Suitable materials include expanded vermiculite and foamed styrene beads. The amount of unavailable free space to be added may be calculated from the following equation:

where g is the fraction of unavailable free space to be incorporated in the solid oxidant by means of an inert solid and wherein the remaining quantities are defined above. "Thus, with a given solid oxidant and given liquid fuel, all quantities are known except g, which may be determined by solving Equation 3.

It has been found that porous materials, such as expanded vermiculite, may absorb some of. the liquid fuel and may exert a desensitizing influence on the blasting agent. In other compositions, it permits liquid com plete blanketing of the mixture while permitting slight positive ox gen balance which may be desirable to increase the sensitivity in certain applications.

It is apparent that both methods may be utilized to achieve an oxygen balanced, completely blanketed blasting agent by using blended liquid fuels and adjusting the free space with inert solids.

The oxidant utilized in the present invention is sodium chlorate alone or mixed with other oxidants, such as ammonium nitrate, sodium nitrate and the like. The particle size or distribution does not appear to be critical provided a uniform mixture is obtainable with liquid fuels and oxygen balance and complete blanketing can be achieved.

Suitable liquid fuels include fuel oil, benzene, toluene, nitromethane, Z-nitropropane, o-nitrotoluene, dinitrotoluene, nitrobenzene and mixtures thereof.

The blasting agents of the invention are preferably mixed in the field at the blasting site. The composition is first determined according to one of the above methods.

The solids are poured into a borehole and the required amount of liquid fuel then poured over the solids to cover the same. An alternative method involves pouring the liquid fuel over the solid oxidant in a vessel and then pouring the mixture from the vessel into the borehole. The latter procedure affords greater homogeneity and uniformity and is preferred for blasting agents which are less sensitive. A suitable booster, such as a block of 50/50 pentolite weighing about 160 grams or the equivalent, is lowered into the borehole while suspended by a detonating fuse so as to be embedded in the blasting agent and is used to detonate the charge.

The sodium chlorate used in the blasting agents of the invention preferably has a particle size in the range of to 150 mesh. In the examples set forth herein the sodium chlorate used had the following particle size distribution.

Mesh size: Percent +20 standard Tyler mesh 0.2 -20 +28 standard Tyler mesh 17.7 28 standard Tyler mesh 45.6 35 +48 standard Tyler mesh 23.00 -48 +65 standard Tyler mesh 6.6 65 +100 standard Tyler mesh 3.3 -100 standard Tyler mesh 3.6

The bulk density of the above chlorate was 1.7:005 g./cc. It had about 30 to 32% available free space.

Sodium chlorate may be used alone or a portion thereof may be replaced with sodium or ammonium nitrate in the range of 20 to 150 mesh. In such mixtures the chlorate comprises to 100% of the mixture and 0 to 60% nitrate. In the examples given herein ammonium nitrate having the following particle size distribution was used.

Standard Tyler. mesh size: Percent +48 6.0 -48 +65 303 -65 +100 17.7 '10o +150 28.8 150 +200 5.3 -200 +325 9.4 325 2.5

Example I The following liquid blanketed blasting agents were prepared and detonated to determine the critical diameters using boosters of 160 grams 50/50 pentolite:

Parts Composition A l B C D Sodium Chlorate 88 88 65. 7 45. 5 Ammonium Nitrate 11.6 45.5 #2 Fuel Oil l2 l2 9 N itro-Benzene. 22. 7

W'ater Expanded vermiculite 0.3 n

Foamed Polystyrene Beads 0.5 Density 1.9 1.7 1.79 1 35 Critic. Diameter finches)". 5 5 9 5 Example 11 The following blasting agents were prepared and detonated with 160 gram 50/ 50 pentolite boosters:

Composition Sodium Chlorate Ammonium Nitrate 2-Nitropropane Critical Diameter (inches) In the above examples wherein water was used as an inert fuel diluent, an emulsifier comprising sodium do- H decyl benzene sulfonate was added in an amount of 1% of the water content. Other emulsifying agents, including alkyl sulfates, alkaryl sulfonates and the like may be used in amounts of 0.1 to 2% of the water content.

There has thus been described liquid fuel blanketed chlorate blasting agents and methods for preparing the same which are highly effective and safe, particularly in the borehole mixing feature.

While the invention has been described in terms of certain examples, they are to be considered illustrative and not limiting and it is intended to cover all modifications and embodiments that fall within the spirit and scope of the appended claims.

We claim:

1. A blasting agent comprising a uniform mixture of sodium chlorate particles and a liquid fuel, said mixture having substantially zero oxygen balance and all available free space between the sodium chlorate particles filled with the liquid fuel. a

2. A blasting agent set forth in claim 1 wherein said liquid fuel is fuel oil.

3. A blasting agent set forth in claim 1 wherein said liquid fuel is a nitro-substitued hydrocarbon.

4. A blasting agent set forth in claim 1 wherein said chlorate contains an inert solid material.

5. A blasting agent set forth in claim 1 wherein said liquid fuel comprises a mixture of liquid fuels.

6. A blasting agent comprising a uniform mixture of a solid particulate oxidant consisting of 40 to by weight of sodium chlorate and 0 to 60% by Weight of ammonium nitrate, and a liquid fuel, said mixture having substantially zero oxygen balance and all available free space between the oxidant particles filled with liquid fuel.

7. A blasting agent comprising a uniform mixture of about 88% by weight of sodium chlorate particles of mesh size in the range of 20 to 150 mesh and having about 30 to 32% available free space, and about 12% by weight of fuel oil, said mixture having substantially zero oxygen balance and all available free space between the sodium chlorate particles filled with the fuel oil.

References Cited in the file of this patent UNITED STATES PATENTS Pennirnan Feb. 10, 1885 Carey Apr. 4, 1944 Barab Apr. 9, 1946 Smith Apr. 5, 1960 Ransom Oct. 24, 1961 Cook et al. July 2, 1963 FOREIGN PATENTS Australia Mar. 27, 1958 

1. A BLASTING AGENT COMPRISING A UNIFORM MIXTURE OF SODIUM CHLORATE PARTICLES AND A LIQUID FUEL, SAID MIXTURE HAVING SUBSTANTIALLY ZERO OXYGEN BALANCE AND ALL AVAILABLE FREE SPACE BETWEEN THE SODIUM CHLORATE PARTICLES FILLED WITH THE LIQUID FUEL. 